In recent years, for the purpose of coping with various use applications, the enhancement of performance, and diversification of a function of an image pickup element have been promoted, and this image pickup element has continued the evolution thereof. Then, one of next generation technologies can include not photoelectric conversion by inorganic semiconductor materials, but photoelectric conversion with organic semiconductor materials. It should be noted that such an image pickup element is referred to as “an organic image pickup element.” In addition, an image pickup element having spectral sensitivities corresponding to a red color, a green color, and a blue color by laminating a plurality of organic semiconductor layers has been being developed (refer to as “a laminated image pickup element”) and has attracted attention. Such a laminated image pickup element requires no color separation optical system, and three kinds of electric signals corresponding to a red color, a green color, and a blue color can be taken out from one pixel. Therefore, light utilization is high, an opening is widened, and a false signal like Moire is hard to occur. It is said that in an image pickup element provided with a normal color filter, transmitted light of approximately 40% is lost.
Incidentally, at present, an image pickup element using silicon (Si) as a photoelectric conversion material is a mainstream. Then, miniaturization of a pixel for enhancement of recording density has progressed, and a size of the pixel has reached approximately 1 μm. A light absorption coefficient of Si is in the range of approximately 103 to approximately 104 cm−1 in the visible light region, and the photoelectric conversion layer in the image pickup element is normally located in a position of 3 μm or more in depth in the silicon semiconductor substrate. Here, when the miniaturization of the pixel size progresses, an aspect ratio between the pixel size and the depth of the photoelectric conversion layer becomes large. As a result, the light leaks from the adjacent pixel(s), and an incidence angle of the light is limited, which leads to reduction of performance of the image pickup element. As the measures taken for solving such a problem, organic materials each having a large absorption coefficient attract attention. The absorption coefficient of each organic material in the visible light region is in the range of approximately 105 cm−1 or more. Thus, in the organic image pickup element or the laminated image pickup element, a thickness of the photoelectric conversion layer can be thinned. For this reason, it is thought that the sensitivity can be enhanced and the number of pixels can be increased while a false color is suppressed, and the development has been earnestly progressed.
In spite of the organic image pickup element which is thought to have many advantages in such a manner, one of problems includes the lowering of a capacitance of an image pickup module. Here, the image pickup module means a device which includes the organic image pickup element built therein, and outputs an electric signal obtained through the photoelectric conversion in the term of an image. The electric charges which are obtained in the photoelectric conversion layer constituting the image pickup element by light irradiation are converted into a voltage which is in turn outputted in the form of an electric signal (image signal). At this time, when in addition to an electric capacitance of the organic image pickup element, a total amount of electric capacitance also including peripheral structures such as floating diffusion (hereinafter, abbreviates as “FD”), and a buffer amplifier connected to FD, and a reset gate and a horizontal output gate adjacent to FD is large, a change in voltage per one electric charge becomes small. Therefore, a signal to noise (S/N) ratio is reduced, and thus the image quality is deteriorated. Here, the voltage V of the electric signal is expressed as follows:V=Q/C 
where Q is an amount of electric charges. After all, when the electric capacitance of the organic image pickup element becomes large, V is reduced and as a result, the electric signal becomes small. It should be noted that the electric capacitance of the organic image pickup element (specifically, an electric capacitance of an organic layer which will be next described) occupies approximately a half of the total amount C of electric capacitance. In addition, in general, the electric capacitance C0 is expressed by the following expression:C0=(ε·S0)/d0 
where ε is a dielectric constant, S0 is an area, and d0 is a thickness. Therefore, the factors which affect the lowering of the capacitance of the organic image pickup element include the dielectric constant of the material constituting the organic image pickup element, and the thickness of the organic layer in the organic image pickup element. Then, when the lowering of the capacitance is realized with the thickness, it is necessary to thick the total thickness of the organic layer of the organic image pickup element.
The organic layer, for example, as depicted in a conceptual view of FIG. 1A, has a laminated structure of a carrier blocking layer (anode-side carrier blocking layer) 22, an organic photoelectric conversion layer 23, and a cathode-side buffer layer 24 which are sandwiched between an anode 21 and a cathode 25. It is possible to thicken a thickness of the organic photoelectric conversion layer 23. However, the organic photoelectric conversion layer 23 is a layer involved in the photoelectric conversion function. Thus, it is difficult in many cases that the increased thickness, and no reduction of the photoelectric conversion efficiency when light having a certain specific wavelength is subjected to the photoelectric conversion are made compatible with each other. In addition, in the case of the laminated image pickup element, when with the spectral characteristics of the material constituting the organic photoelectric conversion layer 23, light other than light having a desired wavelength is also absorbed, if the organic photoelectric conversion layer 23 is thickered, it is feared that the photoelectric conversion layer constituting the image pickup element located below blocks off the light to be absorbed.